Distribution of equipotential surfaces of inductance windings comprising layers with a double series of steps

ABSTRACT

A simply-built device for distributing the potential around a high-voltage output conductor and at the ends of the layers of windings of an inductor coil or of a transformer consisting of windings in layers arranged in a double step configuration on either side of a middle layer which is the shortest and to which is connected the high-voltage output. It consists of cages formed by conductors, each connected to an end of a winding layer by flat conductor grids placed above the layers of winding, and each connected to the end of the layer of wire.

,[151 3,656,077 [451 Apr-.11, 1972 United States Patent Laser et a1. 1

3,353,129 11/1967 Leibinger.................... 3,376,531 4/1968Fisheretal. 1,039,298 9/1912 Kurda.......... 1,942,575 1/1934Shapiro............

[54] DISTRIBUTION OF EQUIPOTENTIAL SURFACES OF INDUCTANCE WINDINGSCOMPRISING LAYERS WITH A DOUBLE SERIES OF STEPS [72] Inventors: GeorgesLaser, Garches; Daniel Bornet,

FOREIGN PATENTS OR APPLICATIONS Paris, both ofFrance 451,319 5/1968Switzerland Alsthom-Savoisienne Sept. 8, 1970 Prim ary Examiner-ThomasJ. Kozma [73] Assignee: [22] Filed:

AttorneySughrue, Rothwell, Mion, Zinn & Ma'cpeak ABSTRACT [21] App1.No.:70,166

distributing the potential around a ge output conductor and at th ds ofA simply-built device for [30] Foreign Application Priority'Data high-yolta I e en the layers of Sept. 8, 1969 ....6930723 a ansfm'er 1 eortest and to which U.S. i connected th hi h lt t t It i t f cages Int.Cl..........................................................I'I0lf rseach connected to an ofa [58] Field ofSw-ch .....................336/84,69, 70; 174/35 CE tor grids placed above the layers 0fwind-' ing, andeach connected to the end of the layer of wire.

7 Claims, 4 Drawing Figures [56] References Cited UNITED STATES PATENTS3,013,102 12/1961 D011 PATENTEUAPR 11 I972 3,656,077

SHEET 3 OF 3 FIGS I kind in which the electrical field of DISTRIBUTIONOF EQUIPOTENTIAL SURFACES OF INDUCTANCE WINDINGS COMPRISING LAYERS WITHA DOUBLE SERIES OF STEPS BACKGROUND OF THE INVENTION device intended todistribute correctly the equipotential electric field surfaces around ahigh-voltage output and at the ends of winding layers which areseries-connected, two by two, and which are arranged in two sequences ofsteps on either side of the middle layer, the less high one, which is atthe highest potential and from which defines the high-voltage output.

2. Description of the Prior Art The maximum electrical stresses are, asa matter of fact, located at the ends of the layers. Different deviceshave been visualized to reduce these localized stresses by distributingthe potential gradient in such a way as to make the electrical fielduniform. French Pat. No. 1,492,630 describes a device of this the outputconductor is directed around this conductor by means of leaf-shapedscreens (paper or metal conductor), arranged concentrically around thisconductor, each connected electrically to one end of the winding layerand embedded in molded parts made of pressed cardboard or otherinsulating materials, This method is very delicate to carry out,especially as regards the metallic coating, due to the very highelectrical gradients which are generated on the leaf-shaped screensection.

SUMMARY OF THE INVENTION This invention pertains to a new deviceintended to distribute correctly the equipotential surfaces. It doesaway with inconvenience and considerably facilitates production whileoffering excellent potential distribution. This device is for thedistribution of the equipotential surfaces of the electrical fieldaround a high-voltage output conductor and at the ends of the windinglayers of an electrical induction apparatus, such as an inductance or atransformer, made up of windings consisting of layers connected inseries, two by two, and distributed symmetrically and forming twosequences of steps on either side of a thin middle layer, which is theshorter one and which bears the high-voltage output. It involves screensmade of conducting material installed concentrically around the outputconductor and each electrically connected to a nearby end of a windinglayer. It is characterized by the fact that these screens are made up ofcages formed by bars made of conducting material and by the fact thatother bars, made of conducting material, define flat grids. ofconcentric elements. Each grid is placed at the end of the assembly oftwo seriesconnected winding layers and are electrically connected to theneighboring end of these two winding layers. It is particularlyadvantageous to select bars made of conducting material having a roundcross section so as to reduce the possible electrical gradients as muchas possible.

These bars are preferably coated with an electrical insulation. Theycan, in advance, be insulated by machine as this helps avoid the coastin insulating the electrostatic screens with sheets from the prior stateof the art. I

These cages are simple to make because they are first shaped flat andthen bent only at the end so as to give them their final cylindricalform.

The effectiveness of the protection offered by the potentialdistribution device is further increased if tubes made of insulatingmaterial are inserted between the .cages.

BRIEF DESCRIPTION OF THE DRAWINGS Referring now to the attachedschematic figures, we will describe examples for the implementation ofthe invention, given here without any restrictions.

FIG. 1 is a perspective view of a very high voltage transformer with apartial cross section showing a winding made up of layers distributedalong two sequences .of steps, equipped with the potential distributiondevice of the present invention;

FIG. 2 is a partial cross section of this, on a larger scale, along aplane passing through the axis of the winding and through thehigh-voltage output conductor;

FIG. 3 is a plan view of a flat formed cage; and

FIG. 4 is'a perspective view of the cage of FIG. 3 after bending, in itsfinal form.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2, awinding made up of a middle layer 1 has on either side of, successively,pairs of layers which are symmetrical to each other, with a growinglength at 2 and 3, 4 and 5. The layers of one pair 2 and 3 or 4 and 5are electrically connected in series, in the known manner by means (notshown). These various winding layers are formed by the spirals of aconducting material, such as 6, surrounded by an insulating coating 7.An output conductor 8 is connected to one end of the middle layer 1which is the layer with the highest voltage.

The output conductor 8 is surrounded by two cages 9 and 10. The firstone made up of bars 11 and of short-circuit rings 12. The second one ismade up of bars 13 and rings 14. These cages are made on the basis ofround conductors which have previously been insulated, for example, bymeans of paper, which have been connected by welding, and which havebeen reinsulated at the places where the attachment has destroyed theinsulation. The assembly is made flat and the developed cage thusobtained is bent to give it its final form.

Cage 9 is then connected to the voltage of layers 2 and 3 by aconnection 15, and cage 10 is connected to the voltage of layers 4 and 5by a connection 16. These connections may be accomplished-by means ofdevices (not shown) which seriesconnect, respectively, layers 2 and 3and 4' and 5. The potentials of the cages thus decrease gradually in adirection away from the output conductor 8.

Between the different cages, such as 9 and 10, and between the outputconductor 8 and the first cage 9, are placed insulating tubes 17 toincrease the effectiveness of protection. These tubes are made ofcomposition board, agglomerated cardboard or any other insulatingsubstance, and are not shown in FIG. 1 so as not to overload FIG. 1. Todirect the equipotential surfaces, metallic armature grids l8 and 19,visible in FIG. 1, are placed, respectively, at the ends of layers 2 and3, on one hand, and 4 and 5 on the other hand, in a series-connectedfashion. These grids have a shape recalling the shape of resistances inelectrical kitchen ranges. They are made up of a round conductor,insulated by paper or some other insulating material, and they areconnected, for example, by welding, to the corresponding cages, that isgrid 18 is connected to cage 9 and grid 19 is connected to cage 10.These grids are the devices that assure the series-connection of thelayers. Grid 19 has spirals situated in the free space between the endsof layers 4 and 5.

In FIGS. 1 and 2, there are shown only two cages and two grids, butthese can obviously be more numerous if the number of layers in thewinding is greater. In FIG, I a supple mentary interior layer 20 hasbeen shown, to which would correspond, another outside layer (notshown), series-connected with the former, and there would also be hereanother cage and another grid, connected to the neutral if this were toinvolve the last layers of the winding.

FIGS. 3 and 4 show another way of making the cages very easily. FIG. 3shows the developed surface of such a cage in the fonn of a serpentine,made up of a conductor 21, insulated, for example, by means of papertaping. This developed surface is then bent and applied on an insulatingcylinder 22,

' FIG. 4, which at the-same time plays the role of support for theconductor 21, forming the cage, and for the insulating tube 17, shown inFIG. 2.

What is claimed is:

short-circuit I windings on either side of a shorter middle windinglayer bearing the high-voltage output conductor, the improvementcomprising:

spaced concentric screens of conducting material surrounding the outputconductor, means connecting each screen to an end of a respectivewinding layer, each of said screens comprising bars of conductingmaterial, and short-circuit rings connecting said bars I concentricconductive gridsoverlying the ends of each winding layer andseries-connected in the same manner as said inductance windingsand beingelectrically connected to corresponding ends of respectiveseries-connected winding layers. 2. The device according to claim 1wherein said bars of conducting material have a round cross section.

3. The device according to claim 1 wherein said bars of conductingmaterial are coated with insulation.

4. The device according to claim 3 further comprising: insulating tubesinserted between said cages and between the output conductor and theinnermost cage. 5. The device according to claim 1, where the screensare of a serpentine configuration formed from a single conducting bar,and wherein the device further includes an insulating cylinder forsupporting each screen.

6. The device according to claim 1, where the spaced concentric screensfurther include short circuit rings connecting the bars at a distancefrom the ends of each winding layer.

7. The device according to claim 6 further including a conductive gridcantilevered from the outermost screen and extending without touchingbetween the spaced ends of the innermost and outennost windings.

1. In an inductance device formed of two by two layers ofseries-connected and symmetrically distributed stepped windings oneither side of a shorter middle winding layer bearing the high-voltageoutput conductor, the improvement comprising: spaced concentric screensof conducting material surrounding the output conductor, meansconnecting each screen to an end of a respective winding layer, each ofsaid screens comprising bars of conducting material, and short-circuitrings connecting said bars concentric conductive grids overlying theends of each winding layer and series-connected in the same manner assaid inductance windings and being electrically connected tocorresponding ends of respective series-connected winding layers.
 2. Thedevice according to claim 1 wherein said bars of conducting materialhave a round cross section.
 3. The device according to claim 1 whereinsaid bars of conducting material are coated with insulation.
 4. Thedevice according to claim 3 further comprising: insulating tubesinserted between said cages and between the output conductor and theinnermost cage.
 5. The device according to claim 1, where the screensare of a serpentine configuration formed from a single conducting bar,and wherein the device further includes an insulating cylinder forsupporting each screen.
 6. The device according to claim 1, where thespaced concentric screens further include short circuit rings connectingthe bars at a distance from the ends of each winding layer.
 7. Thedevice according to claim 6 further including a conductive gridcantilevered from the outermost screen and extending without touchingbetween the spaced ends of the innermost and outermost windings.